I would like to upgrade my iCloud plan from 50GB to 100GB, how do I go about it?

FoxFifth, thank you for telling me that I can’t buy 100GB storage on iCloud. Would you know why? Because I’m just running out of space at 50GB and it took me 4 years to get there, so buying 4 times what I just filled it just doesn’t make sense. Sure it’s only going from $0.99 to $2.99 per month charge, but why should I pay for all this unused space for at least 4-6 years? We are such a wasteful society.

Thank you…